Spinal implants and methods

ABSTRACT

The present invention provides a spinal implant for placement between adjacent processes of the human spine. In some embodiments the spinal implant includes a spacer and one or more retention members. In some embodiments, the retention members are fixed relative to the spacer and in other embodiments the retention members are deployable from a first or compact or stowed position to a second or expanded or deployed position. In some embodiments the spacer is expandable from a first size to a second size. In some embodiments the spacer has a tapered body.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 12/013,351, entitled “SPINAL IMPLANTS AND METHODS” and filed onJan. 11, 2008 which is a continuation-in-part of U.S. patent applicationSer. No. 11/293,438, entitled “INTERSPINOUS DISTRACTION DEVICES ANDASSOCIATED METHODS OF INSERTION” and filed on Dec. 2, 2005, which is acontinuation-in-part of U.S. patent application Ser. No. 11/257,647,entitled “INTERSPINOUS DISTRACTION DEVICES AND ASSOCIATED METHODS OFINSERTION” and filed on Oct. 25, 2005, each of which is incorporated infull by reference herein.

The present application is also a continuation-in-part of U.S. patentapplication Ser. No. 11/934,604, entitled “SPINOUS PROCESS IMPLANTS ANDASSOCIATED METHODS” and filed Nov. 2, 2007 which is incorporated in fullby reference herein.

The present application further claims the benefit of U.S. ProvisionalPatent Application No. 60/884,581, entitled “SPINAL STABILIZATION” andfiled Jan. 11, 2007, U.S. Provisional Patent Application No. 60/621,712,entitled “INTERSPINOUS DISTRACTION DEVICES AND ASSOCIATED METHODS OFINSERTION,” and filed on Oct. 25, 2004; U.S. Provisional PatentApplication No. 60/633,112, entitled “INTERSPINOUS DISTRACTION DEVICESAND ASSOCIATED METHODS OF INSERTION,” and filed on Dec. 3, 2004; U.S.Provisional Patent Application No. 60/639,938, entitled “INTERSPINOUSDISTRACTION DEVICES AND ASSOCIATED METHODS OF INSERTION,” and filed onDec. 29, 2004; U.S. Provisional Patent Application No. 60/654,483,entitled “INTERSPINOUS DISTRACTION DEVICES AND ASSOCIATED METHODS OFINSERTION,” and filed on Feb. 21, 2005; U.S. Provisional PatentApplication No. 60/671,301, entitled “INTERSPINOUS DISTRACTION DEVICESAND ASSOCIATED METHODS OF INSERTION,” and filed on Apr. 14, 2005; U.S.Provisional Patent Application No. 60/678,360, entitled “INTERSPINOUSDISTRACTION DEVICES AND ASSOCIATED METHODS OF INSERTION,” and filed onMay 6, 2005; and U.S. Provisional Application No. 60/912,273; entitled“FUSION PLATE WITH REMOVABLE OR ADJUSTABLE SPIKES” and filed Apr. 17,2007, each of which is incorporated in full by reference herein.

FIELD OF THE INVENTION

The present invention relates to spinal implants and associated methods.

BACKGROUND

The vertebrae of the human spine are arranged in a column with onevertebra on top of the next. An intervertebral disc lies betweenadjacent vertebrae to transmit force between the adjacent vertebrae andprovide a cushion between them. The discs allow the spine to flex andtwist. With age, spinal discs begin to break down, or degenerateresulting in the loss of fluid in the discs and consequently resultingin them becoming less flexible. Likewise, the disks become thinnerallowing the vertebrae to move closer together. Degeneration may alsoresult in tears or cracks in the outer layer, or annulus, of the disc.The disc may begin to bulge outwardly. In more severe cases, the innermaterial of the disc, or nucleus, may actually extrude out of the disc.In addition to degenerative changes in the disc, the spine may undergochanges due to trauma from automobile accidents, falls, heavy lifting,and other activities. Furthermore, in a process known as spinalstenosis, the spinal canal narrows due to excessive bone growth,thickening of tissue in the canal (such as ligament), or both. In all ofthese conditions, the spaces through which the spinal cord and thespinal nerve roots pass may become narrowed leading to pressure on thenerve tissue which can cause pain, numbness, weakness, or even paralysisin various parts of the body. Finally, the facet joints between adjacentvertebrae may degenerate and cause localized and/or radiating pain. Allof the above conditions are collectively referred to herein as spinedisease.

Conventionally, surgeons treat spine disease by attempting to restorethe normal spacing between adjacent vertebrae. This may be sufficient torelieve pressure from affected nerve tissue. However, it is oftennecessary to also surgically remove disc material, bone, or othertissues that impinge on the nerve tissue and/or to debride the facetjoints. Most often, the restoration of vertebral spacing is accomplishedby inserting a rigid spacer made of bone, metal, or plastic into thedisc space between the adjacent vertebrae and allowing the vertebrae togrow together, or fuse, into a single piece of bone. The vertebrae aretypically stabilized during this fusion process with the use of boneplates and/or pedicle screws fastened to the adjacent vertebrae.

Although techniques for placing intervertebral spacers, plates, andpedicle screw fixation systems have become less invasive in recentyears, they still require the placement of hardware deep within thesurgical site adjacent to the spine. Recovery from such surgery canrequire several days of hospitalization and long, slow rehabilitation tonormal activity levels.

More recently, investigators have promoted the use of motionpreservation implants and techniques in which adjacent vertebrae arepermitted to move relative to one another. One such implant that has metwith only limited success is the artificial disc implant. Thesetypically include either a flexible material or a two-piece articulatingjoint inserted in the disc space. Another such implant is the spinousprocess spacer which is inserted between the posteriorly extendingspinous processes of adjacent vertebrae to act as an extension stop andto maintain a minimum spacing between the spinous processes when thespine is in extension. The spinous process spacer allows the adjacentspinous processes to move apart as the spine is flexed.

BRIEF DESCRIPTION OF THE DRAWINGS

Various examples of the present invention will be discussed withreference to the appended drawings. These drawings depict onlyillustrative examples of the invention and are not to be consideredlimiting of its scope.

FIG. 1 is a perspective view of a spinal implant according to thepresent invention;

FIG. 2 is a cross sectional view of the spinal implant of FIG. 1 showingthe implant in a first position;

FIG. 3 is a cross sectional view of the spinal implant of FIG. 1 showingthe implant in a second position;

FIG. 4 is an elevation view of a spinal implant according to the presentinvention showing the implant in a first position;

FIG. 5 is an elevation view of the spinal implant of FIG. 4 showing theimplant in a second position;

FIG. 6 is a perspective view of a spinal implant according to thepresent invention;

FIG. 7 is a cross sectional view of the implant of FIG. 6;

FIG. 8 is a perspective view of a spinal implant according to thepresent invention;

FIG. 9 is a perspective view of a spacer component of the spinal implantof FIG. 8 in a first position;

FIG. 10 is a perspective view of a spacer component of the spinalimplant of FIG. 8 in a second position;

FIG. 11 is an elevation view of a core component of the spinal implantof FIG. 8 in a first position;

FIG. 12 is a perspective view of a spinal implant according to thepresent invention;

FIG. 13 is a perspective view of the spinal implant of FIG. 12illustrating one method of insertion;

FIG. 14 is a perspective view of the spinal implant of FIG. 12illustrating another method of insertion;

FIG. 15 is a perspective view of an alternative configuration for theretention members of the spinal implant of FIG. 12;

FIG. 16 is a perspective view of a spinal implant according to thepresent invention;

FIG. 17 is an elevation view of a spinal implant according to thepresent invention in a first position;

FIG. 18 is an elevation view of the spinal implant of FIG. 17 in asecond position;

FIG. 19 is a perspective detail view of one end of the spinal implant ofFIG. 17 showing the first and second positions superimposed on oneanother

FIG. 20 is a perspective view of a spinal implant according to thepresent invention;

FIG. 21 is a perspective view of the spinal implant of FIG. 20 shownimplanted in a first position;

FIG. 22 is a perspective view of the spinal implant of FIG. 20 shownimplanted in a second position;

FIG. 23 is a perspective view of a spinal implant according to thepresent invention in a first position;

FIG. 24 is a perspective view of the spinal implant of FIG. 23 in asecond position;

FIG. 25 is a perspective view of a spinal implant according to thepresent invention in a first position;

FIG. 26 is a perspective view of the spinal implant of FIG. 24 in asecond position;

FIG. 27 is a perspective view of the spinal implant of FIG. 26 in athird position;

FIG. 28 is a cross sectional view of a spinal implant according to thepresent invention in a first position;

FIG. 29 is a cross sectional view of the spinal implant of FIG. 28 in asecond position;

FIG. 30 is a perspective view of a spinal implant according to thepresent invention in a first position;

FIG. 31 is a side elevation view of the spinal implant of FIG. 30 in thefirst position;

FIG. 32 is a front elevation view of the spinal implant of FIG. 30 inthe first position;

FIG. 33 is a perspective view of the spinal-implant of FIG. 30 in asecond position;

FIG. 34 is a perspective view of a spinal implant according to thepresent invention in a first position;

FIG. 35 is a perspective view of the spinal implant of FIG. 34 in asecond position;

FIG. 36 is a perspective view of the spinal implant of FIG. 34 in athird position;

FIG. 37 is a perspective view of the spinal implant of FIG. 34 implantedin a spine;

FIG. 38 is a perspective view of a spinal implant according to thepresent invention;

FIG. 39 is a front elevation view of the spinal implant of FIG. 38implanted in a spine;

FIG. 40 is a cross sectional view of a spinal implant according to thepresent invention implanted in a spine;

FIG. 41 is a cross sectional view of a spinal implant according to thepresent invention implanted in a spine;

FIG. 42 is a front elevation view of a component of a spinal implantaccording to the present invention being implanted in a spine;

FIG. 43 is a front elevation view of the fully assembled implant of FIG.42 implanted in a spine;

FIG. 44 is a perspective view of a spinal implant according to thepresent invention in a first position;

FIG. 45 is a perspective view of the spinal implant of FIG. 44 in asecond position;

FIG. 46 is a perspective view of the spinal implant of FIG. 44 in athird position;

FIG. 47 is a perspective view of a spinal implant according to thepresent invention in a first position;

FIG. 48 is a perspective view of the spinal implant of FIG. 47 in asecond position;

FIG. 49 is a perspective view of a spinal implant according to thepresent invention in a first position;

FIG. 50 is a side elevation view of the spinal implant of FIG. 49 in asecond position;

FIG. 51 is a perspective view of a spinal implant according to thepresent invention in a first position;

FIG. 52 is a perspective view of the spinal implant of FIG. 51 in asecond position;

FIG. 53 is a perspective view of a spinal implant according to thepresent invention in a first position;

FIG. 54 is a perspective view of the spinal implant of FIG. 53 in asecond position;

FIG. 55 is an exploded perspective view of a spinal implant according tothe present invention;

FIG. 56 is a front elevation view of the spinal implant of FIG. 55 in afirst position;

FIG. 57 is a front elevation view of the spinal implant of FIG. 55 in asecond position

FIG. 58 is an exploded perspective view of a spinal implant according tothe present invention;

FIG. 59 is an exploded perspective view of a spinal implant according tothe present invention;

FIG. 60 is a right perspective view of a spinal implant according to thepresent invention;

FIG. 61 is a left perspective view of the spinal implant of FIG. 60;

FIG. 62 is a left perspective view of a spinal implant according to thepresent invention;

FIG. 63 is a right perspective view of the spinal implant of FIG. 62;

FIG. 64 is a perspective view of a spinal implant according to thepresent invention;

FIG. 65 is a perspective view of a spinal implant according to thepresent invention;

FIG. 66 is a front elevation view of the spinal implant of FIG. 65;

FIG. 67 is a front elevation view of a spinal implant according to thepresent invention;

FIG. 68 is a flow diagram of a method of inserting a spinal implantaccording to the present invention;

FIG. 69 is a front elevation view of a spinal implant according to thepresent invention; and

FIG. 70 is a perspective view of an alternative embodiment of the spinalimplant of FIG. 69.

DESCRIPTION OF THE ILLUSTRATIVE EXAMPLES

Embodiments of spinal implants according to the present inventioninclude a spacer and one or more retention members. Throughout thisspecification, the spinal implant will be referred to in the context ofa spinous process implant. However, it is to be understood that thespinal implant may be configured for insertion into the cervical,thoracic, and/or lumbar spine between adjacent spinous processes,transverse processes, and/or other vertebral structures. The spacer maybe provided in a variety of sizes to accommodate anatomical variationamongst patients and varying degrees of space correction. The spacer mayinclude openings to facilitate tissue in-growth to anchor the spacer tothe vertebral bodies such as tissue in-growth from the spine. Forexample, the spacer may be configured for tissue in-growth from superiorand inferior spinous processes to cause fusion of the adjacent spinousprocesses. The openings may be relatively large and/or communicate to ahollow interior of the spacer. A hollow interior may be configured toreceive bone growth promoting substances such as by packing thesubstances into the hollow interior. The openings may be relativelysmall and/or comprise pores or interconnecting pores over at least aportion of the spacer surface. The openings may be filled with bonegrowth promoting substances.

The spacer may have any suitable cross-sectional shape. For example, itmay be cylindrical, wedge shaped, D-shaped, C-shaped, H-shaped, includeseparated cantilevered beams, and/or any other suitable shape. The shapemay include chamfers, fillets, flats, relief cuts, and/or other featuresto accommodate anatomical features such as for example the laminaeand/or facets.

The spacer may be incompressible, moderately compressible, highlycompressible, convertible from compressible to incompressible, and/orany other configuration. For example, the spacer may be compressibleinto a compact configuration for insertion between adjacent bones andthen expandable to space the bones apart. The spacer may be allowed toflex to provide a resilient cushion between the bones. The spacer may belocked in the expanded condition to prevent it from returning to thecompact configuration.

The retention member may extend transversely from the spacer relative toa spacer longitudinal axis to maintain the spacer between adjacentspinous processes. A single retention member may extend in one or moredirections or multiple extensions may be provided that extend inmultiple directions. One or more retention members may be fixed relativeto the spacer longitudinally and/or radially. One or more retentionmembers may be adjustable relative to the spacer and/or other retentionmembers longitudinally and/or radially to allow the retention members tobe positioned relative to the spinous processes. The retention membersmay be deployable through and/or from within the spacer to allow thespacer to be placed and the retention members deployed in a minimallyinvasive manner. The retention members may include one or more screws,pins, nails, bolts, staples, hooks, plates, wings, bars, extensions,filaments, wires, loops, bands, straps, cables, cords, sutures, and/orother suitable retention member. The retention members may be made ofmetals, metal alloys, polymers, and/or other suitable materials. Theretention members may grip bone and/or soft tissue, abut bone and/orsoft tissue, facilitate tissue ingrowth and/or ongrowth, and/orotherwise retain the implant.

The retention members may cooperate with fasteners engageable with thespinous processes and/or soft tissue. Such fasteners may include one ormore screws, pins, nails, rivets, bolts, staples, hooks, sutures, wires,straps, clamps, spikes, teeth, adhesives, and/or other suitablefasteners. The fasteners may be integrated into the retention members orthey may be modular. The retention members and/or fasteners may beadjustable, replaceable, and/or removable and may be employed in onedirection and/or on one side of the implant or in multiple directionsand/or on multiple sides of the implant to allow tailoring of the kindand quality of fixation of adjacent bones. For example, the implant maybe placed such that it acts only as a spacer between adjacent bones, asan elastic restraint between adjacent bones, or as a rigid fixationbetween adjacent bones. The spacer, retention members, and/or fastenersmay advantageously be made of different materials.

Cerclage may be used to stabilize the spinal implant and/or to provideother benefits. For example, wires, straps, bands, cables, cords, and/orother elongated members may encircle the pedicles, laminae, spinousprocesses, transverse processes, and/or other spinal structures. Thecerclage may be relatively inextensible to provide a hard check to spineflexion or the cerclage may be relatively extensible to provideincreasing resistance to flexion. The cerclage may be relativelyflexible and drapeable such as a woven fabric or it may be relativelyrigid such as a metal band. The cerclage may have shape memoryproperties that cause it to resume a prior set shape after implantation.The cerclage may be independent of the spinous process implant or mayengage it. For example, the cerclage may pass through a hollow interiorof the spinous process implant and/or engage the extension.

The implant may be supplemented with bone growth promoting substances tofacilitate fusion of adjacent vertebrae between spinous processes,laminae, transverse processes, facets, and/or other spinal structures.The bone growth promoting substances may be spaced from the implant,placed adjacent the implant, sandwiched between the implant andunderlying bone, placed inside the implant, coated onto the implant,and/or otherwise placed relative to the implant. If it is coated ontothe implant it may cover the entire implant or only selected portions ofthe implant such as the spacer, retention members, fasteners, and/orother portions.

As used herein, bone growth promoting substances may include bone paste,bone chips, bone strips, structural bone grafts, platelet derived growthfactors, bone marrow aspirate, stem cells, bone growth proteins, bonegrowth peptides, bone attachment proteins, bone attachment peptides,hydroxylapatite, calcium phosphate, statins, and/or other suitable bonegrowth promoting substances.

The spinal implant and any associated cerclage or other components maybe made of any suitable biocompatible material including among othersmetals, resorbable ceramics, non-resorbable ceramics, resorbablepolymers, and non-resorbable polymers. Some specific examples includestainless steel, titanium and its alloys including nickel-titaniumalloys, tantalum, hydroxylapatite, calcium phosphate, bone, zirconia,alumina, carbon, bioglass, polyesters, polylactic acid, polyglycolicacid, polyolefins, polyamides, polyimides, polyacrylates, polyketones,fluropolymers, and/or other suitable biocompatible materials andcombinations thereof.

The spinal implant may be used to treat spine disease in a variety ofsurgical techniques including superspinous ligament sacrificingposterior approaches, superspinous ligament preserving posteriorapproaches, lateral approaches, and/or other suitable approaches. Thespinal implant may be used to treat spine disease by fusing adjacentvertebrae or by preserving motion between adjacent vertebrae. It mayinclude only an extension stop such as a spacer, only a flexion stopsuch as flexible cerclage elements, or both a flexion and extensionstop. The spinous process implant may be used to reduce loads on thefacet joints, increase spinous process spacing, reduce loads on thedisc, increase disc spacing, and/or otherwise treat spine disease.Techniques for the spinal implant may include leaving the tissues at thesurgical site unmodified or modifying tissues such as trimming, rasping,roughening, and/or otherwise modifying tissues at the implant site.

For example, FIGS. 1-3 illustrate a spinal implant 100 including aspacer 102 and a plurality of retention members in the form of first andsecond plate extensions 104, 105 and deployable retention members 106,108, and 110. The spacer 102 has a generally cylindrical body 112 havinga proximal end 114, a distal end 116, and a longitudinal spacer axis 118extending therebetween. The distal end 116 tapers to an edge tofacilitate inserting the spacer 102 between two bones, e.g. adjacentspinous processes. The distal end is defined by a superior facet 120, aninferior facet 122, and lateral facets 124 (one shown).

The first plate extension 104 projects radially outwardly from thespacer 102 adjacent the proximal end and the second plate extension 105projects radially outwardly from the spacer 102 opposite the first plateextension 104. The plate extensions 104, 105 may be integral with thespacer 102 as shown in FIGS. 1-3 or modular and separable from thespacer 102. The plate extensions 104, 105 provide an insertion stop byabutting the spinous processes 126, 128.

The deployable retention members 106, 108, 110 may be pre-installedwithin the spacer 102 or inserted into the spacer 102 intraoperatively.Preferably they are pre-installed and retracted within the spacer 102 asshown in FIG. 2. Each deployable retention member 106, 108, 110 isdirected into a channel 130, 132, 134 that communicates from theinterior of the spacer 102 out through the distal end 116 to theexterior of the spacer 102. The deployable retention members 106, 108,110 are joined at their proximal ends 136 so that they move together.The interior of the spacer includes a cavity 137 that houses thedeployable retention members 106, 108, 110 in the un-deployed position.The cavity 137 is threaded and receive an actuator screw 138 in axialtranslating relationship.

In use, the spinal implant 100 is inserted between adjacent spinousprocesses 126, 128 as shown. The actuator screw 138 is then rotated sothat it translates along the spacer axis 118 and pushes the deployableretention members 106, 108, 110 distally through the channels 130, 132,134. The spacer 102 includes a pair of sockets 139 at its proximal end114 for receiving a tool for applying a counter torque to the spacer 102while the actuator screw 138 is rotated. The channels 130, 132, 134 maybe curved to cause the deployable retention members 106, 108, 110 tobend away from the spacer axis 118 and grip the spinous processes 126,128 and/or surrounding soft tissue. The deployable retention members106, 108, 110 may also be pre-bent and then elastically straightened asthey are loaded into the un-deployed position of FIG. 2. Upon beingdeployed, they may then return to their pre-bent shape. The deployableretention members 106, 108, 110 may advantageously be made of asuperelastic material such as Nitinol. They may also respond to thepatient's body temperature to change shape from the straightconfiguration of FIG. 2 to the curved configuration of FIG. 3. Softtissue may also grow around, adhere to, scar around, and/or otherwisegrip the deployable retention members 106, 108, 110 over time.Deployable retention member 110 is split at its distal-end to form aloop 140 that opens upon being deployed from the spacer 102 tofacilitate tissue growth into and around the loop 140 for increasedretention strength. A plurality of holes 142 are formed through theplate extensions 104, 105 for receiving fasteners for attaching theplate extensions 104, 105 to the surrounding bone and/or soft tissue.Such fasteners may include any of the fasteners listed above. A pin 144is shown in one of the holes 142 in FIG. 3.

FIGS. 4-5 illustrate a spinal implant 200 similar in form and functionto that of FIGS. 1-3. The spinal implant 200 includes a spacer 202,deployable retention members 204, and spacer end pieces 206. The spacer202 and end pieces 206 are generally cylindrical and are aligned along aspacer axis 208 and connected by a threaded shaft 210 that threadablyengages the end pieces 206. The threaded shaft 210 is mounted to thespacer 202 for axial rotation and includes a driver engaging end 212.The deployable retention members 204 are fixed in the spacer 202 and areslidably received in channels 214 in the end pieces 206.

In use, the spinal implant 200 is inserted between adjacent bones suchas spinous processes 220, 222. A driver (not shown) is engaged with thedriver engaging end 212 of the threaded shaft 210 and rotated to movethe end pieces 206 toward the spacer 202 causing the retention members204 to extend out of the channels 214 away from the spacer axis 208 asshown in FIG. 5. A tool (not shown) may be engaged with one or moresockets 224 in one of the end pieces 206 or notches 226 in the spacer202 to apply a counter torque while the threaded shaft 210 is rotated.

FIGS. 6-7 illustrate a spinal implant 300 similar in form and functionto that of FIGS. 1-3. The spinal implant 300 includes a spacer 302, acore 304, and deployable retention members 306 extending from the core304. The deployable retention members 306 include a plurality of wiresprojecting in a radial array from a core/spacer axis 308 at each end ofthe core 304. In the illustrative example, which have been designed forinterspinous placement, there are no wires projecting anteriorly toavoid impingement with the facets and/or other spinal structures. Thecore 304 and deployable retention members 306 are received in apassageway 309 through the spacer 302 parallel to the spacer axis 308.

In use, the spacer 302 is positioned between adjacent bones such asspinous processes 310, 312. The core 304 and deployable retentionmembers 306 may be partially pre-inserted as shown in FIG. 7 such thatafter the spacer 302 is positioned the core is advanced to deploy thedeployable retention members 306. Alternatively, the core and deployableretention members 306 may be separate from the spacer 302 and insertedafter the spacer is placed. In either case, a tube 314 may optionally beused to hold the deployable retention members 306 and/or core 304 priorto deployment. As shown in FIG. 7, the tube 314 may be engaged with thespacer 302 in alignment with the passageway 309 and the core 304 anddeployable retention members 306 pushed from the tube 314 into thepassageway 309 until the deployable retention members 306 deploy fromthe opposite end of the passageway 309. The tube 314 may be withdrawn topermit the remaining deployable retention members 306 to deploy.

FIGS. 8-11 illustrate a spinal implant 400 similar in form and functionto that of FIGS. 1-3. The spinal implant 400 includes a generallycylindrical hollow spacer 402 having a first end 404, a second end 406,and a spacer axis 408 extending from the first end 404 to the second end406. A core 410 is positionable within the spacer 402 along the spaceraxis 408. Optionally, a plurality of deployable retention members 412project radially away from the spacer axis 408 at each end of the core410. The spacer 402 is made of a compressible material such as asuperelastic metal or polymer such that it can be compressed tofacilitate insertion. For example, as shown in FIG. 9, the prongs 420 ofa tool (not shown) may be inserted into the spacer 402 and spread apartto stretch the spacer 402 into a flattened elliptical shape. The spacer402 may then be inserted and the prongs removed to allow the spacer 402to recover to its original shape. Depending on the modulus of the spacer402 and the loads exerted on it by the surrounding bones, it may recoverto its full pre-insertion height and distract the bones or it may onlyrecover partially. The core 410 may then be inserted to maintain thespacer 402 at its recovered height. The core 410 may be sized to pressinto the spacer 402 and thereby prevent any compression of the spacer402 post-insertion or the core may be sized to allow a predeterminedamount of compression of the spacer 402 to provide a resilient spacer.The optional deployable retention members 412 may be omitted and thespinal implant 400 used in the condition shown in FIG. 10. Preferably,the core 410 includes deployable retention members 412 in the form offilaments that can be deployed as an array of loops projecting radiallyoutwardly from the spacer axis 408 at each end of the core 410. Theretention members 412 may retain the space 402 in place by physicallyblocking withdrawal. The retention members 412 may also retain thespacer 402 due to tissue growth around the retaining members 412.

FIG. 11 illustrates one way of arranging the deployable retentionmembers 412. A plurality of rings 422 are mounted on the core 410 withat least one of the rings 422 being axially translatable along the core410. The rings are connected by a plurality of filaments 424 spiralingaround the core 410.

In use, the spacer 402 is inserted between adjacent bones such asadjacent spinous processes and the core 410 is inserted into the spacer402. At least one ring 422 is moved toward another ring 422 causing thefilaments 424 to bend away from the core and form the array of loops asshown in FIG. 8. Alternatively, the retaining members 412 may be foldeddown parallel to the spacer axis 408 similar to the embodiment of FIG.7.

FIGS. 12-14 illustrate a spinal implant 500 similar in form and functionto that of FIGS. 1-3. The spinal implant 500 includes a spacer 502having a generally cylindrical hollow body 504 including a first end506, a second end 508, and a spacer axis 510 extending from the firstend 506 to the second end 508. The ends of the spacer 502 are tapered tofacilitate insertion between adjacent bones. A plurality of channels 512extend through the body 504 from the first end 506 to the second end 508generally parallel to the spacer axis 510. Deployable retention members514 are engageable with channels 512 in axially slidable relationship.In the illustrative example of FIGS. 12-14, the channels 512 anddeployable retention members 514 have complimentary rectangular crosssectional shapes. The deployable retention members 514 are curved toextend radially away from the spacer axis 510 and grip the spinousprocesses.

In use, the deployable retention members 514 are straightened and/orretracted to allow the spinal implant 500 to be inserted between thespinous processes. This may be accomplished in a variety of ways. Asshown in FIG. 13, the deployable retention members 514 may be withdrawnpartway through the channels 512 forcing them to straighten. They mayinclude a stop to prevent them from being withdrawn completely. Afterthe spacer 502 is inserted between the spinous processes, the deployableretention members 514 may be fed through the channels 512 and allowed toresume their curved configuration. Alternatively the deployableretention members 514 may be separated from the spacer 502 completelyand not introduced until after the spacer 502 has been inserted. Asshown in FIG. 14, the deployable retention members 514 may bestraightened and the spinal implant 500 inserted through a tube 520 andinto the space between the spinous processes. FIG. 12 illustrates thespinal implant 500 post-insertion with the deployable retention members514 fully deployed. FIG. 15 illustrates a spinal implant 600 similar tothat of FIGS. 12-14. Spinal implant 600 has deployable retention members602 in the form of wires rather than the rectangular ribbon-likedeployable retention members 514 of FIGS. 12-14.

FIG. 16 illustrates a spinal implant 700 similar to that of FIGS. 12-14.Spinal implant 700 includes a spacer 702 having a passageway 704 throughthe spacer 702 parallel to a spacer axis 706. After the spacer 702 isinserted between adjacent spinous processes, a preformed deployableretention member 708 in the form of a wire is inserted through thepassageway 704 from a first end to a second end of the passageway sothat it emerges from the second end and returns to its preformed shapeto extend transverse to the spacer axis 706 beyond the outer surface ofthe spacer 702. The end of the deployable retention member may alsoextend transverse to spacer axis 706 at the first end of the spacer axisso that the deployable retention member may extend on both sides of aprocess to capture the process. Alternatively, a set screw or othermechanism may be provided to fix the deployable retention member 708 inthe passageway 704 after the deployable retention member 708 has beendeployed. In the illustrative embodiment the deployable retention member708 is preformed into a coil.

FIGS. 17-19 illustrate a spinal implant 800 similar to the previousembodiments. The spinal implant 800 includes a spacer 802 having firstand second ends 804, 806 and a spacer axis 808 extending therebetween.The spacer 802 may be wedge shaped, cylindrical, elliptical,rectangular, and/or any other suitable shape. The shape may be based onanatomical considerations. Deployable retention members are provided inthe form of a terminal portion 810, 812 extending from each end 804, 806of the spacer 802. The terminal portions 810, 812 have a compactposition or shape closer to the spacer axis 808 as shown in FIG. 17 andan expanded position or shape further from the spacer axis 808 as shownin FIG. 18. FIG. 19 illustrates the compact and expanded positionssuperimposed for comparison. In the illustrative embodiment of FIGS.17-19 the terminal portions 810, 812 are provided as coils such as aconventional helical spring coil and the compact position corresponds toa coil being tightly wound and the expanded position corresponds to thecoil being loosely wound. However, the terminal portions 810, 812 may beshaped as a flange, solid disc, protrusion, bar, or the like as a matterof design choice. The spinal implant 800 is implanted with at least oneof the terminal portions 810, 812 in the compact position. Once placed,one or both terminal portions are allowed to expand. For example, thecoils may unwind due to their own spring tension. Alternatively, thecoils may be activated, such as e.g. by heat, to expand. The spacer 802separates adjacent spinous processes and the expanded terminal portions810, 812 maintain the spacer 802 between the spinous processes.

While the terminal portions 810, 812 may be separate devices, in theillustrative embodiment of FIGS. 17-19, the terminal portions 810, 812are connected through a passageway 814 formed through the spacer 802along the spacer axis 808. In this embodiment, the terminal portions810, 812 are the ends of a continuous coil placed within the passageway814. The coil may be designed to be in tension such that the terminalportions tend to seat against the spinous processes to hold the spacer802 firmly in place.

The termination portions 810, 812 may be formed of any number ofmaterials, but superelastic materials such as shape memory metal alloysor polymers are advantageous. In particular, shape memory materials canbe designed having a first small shape to allow less traumaticimplantation of the device. Once implanted, activation of the shapememory material would cause the terminal portions 810, 812 to move fromthe compact position to the expanded position. Moreover, for acontinuous coil embodiment, the coil may be configured to retract andthereby seat the terminal portions against the spinous process.

The spacer 802 may be provided with one or more surface grooves 816 toreceive, e.g., the prongs of a surgical distraction tool so that thespacer may be placed along the prongs after the spinous processes havebeen distracted.

FIGS. 20-22 illustrate an alternative arrangement to that of FIGS. 17-19in which a spinal implant 900 includes a spacer 902 and a coil 904wrapped around the outside of the spacer 902. The coil 904 may haveshape memory properties allowing it to be transformed from a compactposition to an expanded position or it may always be biased toward theexpanded position. In the case where it is always biased toward theexpanded position, the coil 904 may be maintained in the compactposition by a sleeve 906 or other surrounding structure. The spinalimplant 900 is placed between adjacent bones, e.g. spinous processes910, 912, in the compact position (FIG. 21) and allowed, or activated,to transition to the expanded position (FIG. 22) to maintain the spacer902 between the bones. Alternatively, the spacer 902 may be removedafter the spinal implant is implanted or the spacer 902 may be omittedentirely such that just the coil 904 serves as both a spacer andretention member.

FIGS. 23-24 illustrate a spinal implant 1000 including a spacer 1002having a proximal end 1004, a distal end 1006, and a spacer axis 1008extending therebetween. Optionally, the distal end 1006 may be taperedas shown to facilitate insertion between adjacent bones. The spinalimplant 1000 includes one or more deployable retention members mountedfor rotation to the spacer 1002 for rotation between a compact or stowedposition (FIG. 23) and an expanded or deployed position (FIG. 24). Inthe illustrative embodiment of FIGS. 23-24, the deployable retentionmembers are in the form of wires 1010 mounted to brackets 1012 extendingradially away from the spacer axis 1008. The wires 1010 extend betweenthe brackets 1012 generally parallel to the spacer axis 1008 and thenbend transverse to the spacer axis 1008 at the proximal and distal ends1004, 1006. The spacer 1002 includes an annular groove 1014 adjacent thedistal end and the wires 1010 are curved distally to engage the groove1014 in the compact or stowed position. As shown in FIG. 23, the groove1014 may receive the wires 1010 so that their curved portions arecompletely recessed to ease implantation. The proximal ends of the wires1010 are positioned behind the proximal end 1004 of the spacer 1002 inthe compact or stowed position to ease implantation. After the spinalimplant 1000 is inserted between adjacent bones, e.g. spinous processes,the wires 1010 are rotated from the stowed position to the deployedposition to maintain the spacer 1002 between the bones. In theillustrative embodiment of FIGS. 23-24 the proximal ends of the wirescan be accessed after implantation to rotate the wires 1010. The wiresmay maintain their position due to friction with the brackets 1012 or anadditional locking mechanism may be provided. For example, detents 1016may be provided to receive the wires and help maintain them in position,e.g. in the deployed position.

FIGS. 25-27 illustrate a spinal implant 1100 including a spacer 1102having a first end 1104, a second end 1106, and a spacer axis 1108extending therebetween. One or more deployable retention members in theform of end pieces are mounted to the spacer 1102 for rotation between astowed position nearer the spacer axis 1108 and a deployed positionfurther from the spacer axis. For example, the spinal implant mayinclude a pair of outer end pieces 1110 and a pair of inner end pieces1112 with one outer and one inner end piece at each end of the spacer.The outer end pieces 1110 are mounted for rotation about an axis 1114offset from the spacer axis 1108 so that they move nearer to or furtherfrom the spacer axis 1108 as they rotate. For example, the outer endpieces 1110 may be mounted on a common shaft 1116 so that they rotatetogether. The inner end pieces 1112 may be similarly mounted forrotation about an offset axis 1118 on a common shaft 1120. Preferablythe inner pieces 1112 are mounted on a shaft 1120 that is offset fromboth the spacer axis 1108 and the shaft 1116 that the outer end pieces1110 are mounted on so that the inner and outer end pieces 1112, 1110move away from the spacer axis 1108 in different directions. In theexample of FIGS. 25-27, the inner end pieces 1112 have been relieve;e.g. to include notches 1122 (FIG. 27); to clear the shaft of the outerend pieces 1110 so that they may be rotated to a stowed position that iscoaxial with the spacer 1102 as shown in FIG. 25. In use, the spinalimplant 1100 is inserted between adjacent bones, e.g. spinous processes,in the stowed position of FIG. 25. Once the spacer 1102 is in thedesired location one or more of the outer and inner end pieces 1110,1112 may be rotated to the deployed position to maintain the spacer 1102in position. Driver engaging sockets 1124 are provided to facilitaterotating the end pieces. Any number of end pieces may be provided up toand including an implant 1100 in which the entire spacer is made up of aseries of end pieces. The end pieces may be selectively rotated toachieve the desired fit with the adjacent bones. The end pieces may bemounted to separate shafts or otherwise mounted for independentrotation. The end pieces may be mounted to a shaft so that they slipwhen a torque threshold is met. For example, the end pieces may bemounted for predetermined slipping such that if a plurality of endpieces are being rotated together on a common shaft and one abuts abone, the abutting end piece may slip on the shaft and thereby permitthe other end pieces to be rotated fully into the deployed position.

FIGS. 28-29 illustrate a spinal implant 1200 similar to that of FIGS.25-27. The spinal implant 1200 includes a spacer 1202, a proximal end1204, a distal end 1206, and a spacer axis 1208 extending therebetween.A fixed retention member in the form of a plate or bar shaped extension1210 extends radially away from the spacer axis 1208 adjacent theproximal end 1204. A deployable retention member in the form of an endpiece 1212 is mounted at the distal end 1206; The end piece. 1212 ispreferably tapered as shown to facilitate insertion between adjacentbones. The end piece 1212 is mounted to the spacer 1202 for rotationabout an end piece rotation axis 1214 transverse to the spacer axis1208. For example, the distal end 1206 of the spacer may include adistal face 1216 transverse to the spacer axis 1208 and a trunnion 1218projecting outwardly normal to the distal face 1216. The end piece 1212includes a complimentary proximal face 1220 with a socket 1222 forreceiving the trunnion 1218. The end piece 1212 is rotatable about therotation axis 1214 from a compact or stowed position as shown in FIG. 28in which the end piece 1212 extends generally parallel to the spaceraxis 1288 to an expanded or deployed position as shown in FIG. 29 inwhich the end piece 212 extends generally transverse to the spacer axis1208. To facilitate rotation of the end piece 1212, a shaft 1224 extendsfrom the end piece 1212 through a passageway 1226 in the spacer 1202 tothe proximal end 1204. The shaft 1224 may extend parallel to therotation axis 1214 or it may bend as shown. A bent shaft may include aflexible portion, a universal joint, a bevel gear, and/or some otherarrangement to permit transmitting torque through the bend. A driverengaging socket 1228 is provided at the end of the shaft to engage atool for rotating the end piece.

FIGS. 30-33 illustrate a spinal implant 1300 similar to that of FIGS.28-29. The spinal implant 1300 includes a spacer 1302 having a proximalend 1304, a distal end 1306, and a spacer axis 1308 extendingtherebetween. A plurality of deployable retention members are providedat each end in the form end pieces 1310, 1312 mounted for rotation aboutaxes transverse to the spacer axis 1308. As revealed through the brokenaway portion of the spacer 1302 in FIG. 30, the end pieces are mountedto gears 1314 that engage additional gears 1316 on a drive shaft 1318.As the drive shaft 1318 is rotated, the end pieces 1310, 1312 rotateaway from the spacer axis 1308 from the stowed position of FIGS. 30-32to the deployed position of FIG. 33.

FIGS. 34-37 illustrate another spinal implant 1400 including a spacer1402 having a first end 1404, a second end 1406, and a spacer axis 1408extending therebetween. The spacer 1402 is in the form of a cylinder,rectangle, wedge, cone, and/or some other suitable shape and iscompressible transverse to the spacer axis 1408. In the illustrativeexample of FIGS. 34-37 the spacer is hollow and made of an elasticmaterial, preferably a superelastic and/or shape memory material. Thespinal implant 1400 includes one or more arms 1410 extending away fromthe ends 1404, 1406 of the spacer 1402. The arms are also preferablymade of an elastic material such as a superelastic and/or shape memorymaterial. In a compact or stowed position (FIG. 34), the spacer 1402 iscompressed radially toward the spacer axis 1408 and the arms 1410 extendoutwardly generally parallel to the spacer axis 1408. In an expanded ordeployed position (FIG. 36) the spacer 1402 is expanded away from thespacer axis 1408 and the arms 1410 extend transverse to the spacer axis1408. In use, the spinal implant 1400 is inserted between adjacentbones; e.g. spinous processes 1420, 1422; in the compact position andthen allowed or activated to transition to the expanded position (FIG.37). In the illustrative example of FIGS. 34-37, the arms 1410 have apre-formed shape in which they arch or curve back over the spacer 1402to grip the spinous processes. In the illustrative example, the arms1410 also have holes 1424 to receive fasteners similar to the embodimentof FIGS. 1-3. The spacer 1402 may also receive a core (not shown) tomaintain a minimum expanded height similar to the embodiment of FIGS.9-12.

FIGS. 38-39 illustrate a spinal implant 1500 including a spacer 1502having one or more holes 1504 to receive fasteners similar to theembodiment of FIGS. 1-3. In the illustrative example of FIGS. 38-39, thespacer 1502 is a hollow cylinder with the holes 1504 extending throughthe wall of the cylinder and being arrayed around the ends of the spacer1502. The spacer 1502 may be secured by placing fasteners through theholes 1504 and into one or more adjacent bones and/or into surroundingsoft tissue. The spacer 1502 may be secured at one end, at both ends, totissue associated with one adjacent bone, to tissue associated withmultiple adjacent bones, and/or any combination of securingarrangements. In the example of FIG. 39, the spacer 1502 is placedbetween adjacent spinous processes and sutured to the surrounding softtissue 1506 at both ends.

FIG. 40 illustrates a spinal implant 1600 similar to that of FIGS.38-39. The spinal implant 1600 includes a generally solid spacer 1602and includes one or more transverse passageways 1604 for receiving oneor more fasteners 1606. Preferably the passageways 1604 communicate fromthe end of the spacer to the outer surface of the spacer transverse tothe spacer axis as shown. The spacer 1602 may be attached to oneadjacent bone, both adjacent bones, from one side or from two sides. Forexample, in a unilateral procedure a fastener may be placed into onlyone bone to maintain the spacer 1602 in position. Alternatively afastener may be placed into each of the adjacent bones to maintain thespacer 1602 in position and also to hold the adjacent bones in positionrelative to one another. In the example of FIG. 40, screws are placedfrom each side of the spacer 1602 into adjacent spinous processes 1610,1612.

FIG. 41 illustrates a spinal implant 1700 similar to that of FIG. 40.Spinal implant 1700 includes a spacer 1702, a retention member in theform of a flange 1704, and holes 1706 through the flange for receivingfasteners 1708. The holes 1706 may be parallel to the spacer axis (asshown) or transverse to the spacer axis.

FIGS. 42-43 illustrate a spinal implant 1800 including a base 1802having a base axis 1804 and a hook 1806 having a portion 1808 extendinggenerally transversely away from the base axis 1804 and a portion 1810extending generally parallel to the base axis 1804. The spinal implant1800 further includes a spacer 1812 engageable with the base 1802. Thespacer 1812 may be cylindrical, rectangular, conical, and/or any othersuitable shape. In the illustrative example of FIGS. 42-43, the spacer1812 is generally conical and threadably engages the base 1802 in axialtranslating relationship. In use, the hook 1806 is placed around aportion of one or more adjacent bones, e.g. it may be inserted betweenadjacent spinous processes to catch on one of the spinous processes asshown in FIG. 42. The spacer spaces them apart a desired distance asshown in FIG. 43. The spinal implant 1800 allows unilateral andminimally invasive placement like the previous examples and adjustablespacing determined by the axial position of the conical spacer 1812.

FIGS. 44-46 illustrate a spinal implant 1900 including a spacer 1902 anddeployable retention members 1904. The spacer 1902 includes a split body1906 having a superior surface 1908 and an inferior surface 1910. Thesuperior surface 1908 and inferior surface 1910 are movably connected toa driver 1912. The driver 1912 has a screw 1914 attached to it andextending from the driver 1912 between the superior surface 1908 andinferior surface 1910 into a threaded bore 1916 in a wedge 1918. Inoperation, turning the driver 1912 causes the screw 1914 to thread intothe bore 1916, which causes the wedge 1918 to move between the superiorsurface 1908 and the inferior surface 1910. As the wedge 1918 movesfurther between the surfaces 1908, 1910, the surfaces 1908, 1910separate to increase the height of the spacer 1902. Combinations ofchannels 1920 and ribs 1922 provide stabilization for movement of thewedge 1918 relative to the surfaces 1908, 1910. Retention of the spacer1902 may be accomplished using the coils, flanges, discs, wires and/orother protrusions described above. For example, deployable retentionmembers 1904 in the of form elastic wires that may be folded parallel tothe spacer axis 1924 for insertion may provide lateral retention of thespacer 1902.

FIGS. 47-48 illustrate a spinal implant 2000 including a spacer 2002.The spacer 2002 is generally shaped as a cylinder or sleeve having abore 2004. A gap 2006, or slot, extends the length of spacer 2002. Bore2004 may be a complete through bore or bore 2004 may allow for a centralwall or plug (not shown) for stability. Spinal implant 2000 furthercomprises end caps 2010 having a generally conical shape or wedge shape.As end caps 2010 are pressed or threaded into bore 2004, the shape ofcaps 2010 causes the diameter of spacer 2002 to expand, which is allowedbecause of gap 2006. Gap 2006 could be filled with a suitable elasticmaterial. Alternatively to shaped caps 2010, caps 2010 could be made ofan expandable material, such as shape memory alloys, spring steel,resins, polymers or the like to achieve the same result. Lateralretention of the spacer may be accomplished using the coils, flanges,discs, wires and/or other protrusions described above and below and willnot be re-described relative to this embodiment.

FIGS. 49-50 illustrate a spinal implant 2100 similar to that of FIGS.47-48. The spinal implant 2100 has a spacer 2102 in the form of a coiledsheet. The spacer 2102 is moveable from a compact position (FIG. 49) inwhich the coil winds around itself multiple times and is closer to aspacer axis 2104 to an expanded position (FIG. 50) by uncoiling thespacer such that it winds around itself fewer times and is further fromthe spacer axis 2104, e.g. such that it forms a single continuous ring.The spacer has inner and outer hook shaped edges 2106, 2108 that canengage as shown in FIG. 50 to limit the amount of expansion of thespacer 2102. The spinal implant 2100 may also include plugs or cores asshown in prior examples to support the spacer 2102 against collapse.Lateral retention of the spacer may be accomplished using the coils,flanges, discs, wires and/or other protrusions described above and belowand will not be re-described relative to this embodiment.

FIGS. 51-52 illustrate a spinal implant 2200 similar to that of FIGS.49-50. The spinal implant 2200 includes a coiled sheet-like spacer 2202having tabs 2204 projecting away from the sheet to engage slots 2206 tolimit the amount of expansion of the spacer 2202. The tabs 2204 and/orslots 2206 may be positioned at the inner and outer edges of the coiledspacer 2202 or they may be positioned at one or more positionsintermediate the edges. For example, the spacer may have tabs 2204 atone end and slots placed at multiple locations to allow the spacer to befixed at different sizes. The spinal implant 2200 may also include plugsor cores as shown in prior examples to support the spacer 2202 againstcollapse. Lateral retention of the spacer may be accomplished using thecoils, flanges, discs, wires and/or other protrusions described aboveand below and will not be re-described relative to this embodiment.

FIGS. 53-54 illustrate a spinal implant 2300 including a spacer 2302,having a spacer axis 2303, formed of an elastic material, such as apolymer or resin material. For example, the spacer 2302 may be ahydrogel or other composite or polymer material such as a siliconematerial. A bore 2304 extends through the spacer 2302 into a base 2306.The base 2306 is shown with a wedge or conical shape to facilitateinsertion but which could be any shape including rounded or blunt.Deployable retention members in the form of elastic arms 2308 areattached to the base 2306. In use, the base 2306 is inserted betweenadjacent bones, e.g. spinous processes, parallel to the spacer axis2303. As the arms 2308 pass the spinous process, they fold into acompact or stowed insertion position in which they are nearer the spaceraxis 2303 and lie along the sides of the spacer 2302 generally parallelto the spacer axis (FIG. 53). Once the arms 2308 pass the spinousprocess, they return to an expanded or deployed retention position inwhich they project outwardly transverse to the spacer axis 2303 (FIG.54). Preferably, the arms 2308 only fold in one direction to provideincreased retention once inserted. The spinal implant 2300 furtherincludes a plate 2310 having a projection 2312, such as a threadedshaft, extendable through the bore 2304 and threadably engaging the base2306. Threading, for example, the screw into the base 2306 compressesthe spacer 2302 causing the diameter of the spacer 2302 to increase,providing distracting forces on the spinous process. Lateral stabilityis provided by the plate 2310 and the arms 2308 which extend away fromthe spacer axis 2303 on either side of the spinous process.

Alternatively to screw threading into the base 2306, a bolt may beattached to the base and the plate 2310 and spacer 2302 compressed witha nut 2314. Other mechanisms could also be used to compress the spacer2302 including ratchets, press fits, rivets, and/or any other suitablemechanism.

FIGS. 55-57 illustrate a spinal implant 2400 including a base plate 2402and a wedge plate 2404. The base plate 2402 is shown as having arectangular shape, but any shape is possible including, circular,elliptical, square, semi-circular, triangular, trapezoidal, random orthe like. The base plate 2402 has a through hole 2406 (square in theexample shown) and two attachment tabs 2408. The attachment tabs havebores 2410.

The wedge plate 2404 is shown as having a rectangular shape similar tothe base plate 2402, but the base plate 2402 and wedge plate 2404 do notnecessarily have the same shape. Moreover, the wedge plate 2404 may havenumerous possible shapes as explained with reference to the base plate2402. A wedge protrusion 2414 extends from a first side of the wedgeplate 2404. The wedge protrusion 2414 is shown with a generallytriangular shape having a straight side, but other shapes are possibleincluding sides that are rounded, beveled, curved, arched, convex,concave, or the like. The wedge protrusion 2414 has a superior surface2416 and an inferior surface 2418 that generally converge as they travelaway from the wedge plate 2404. The wedge protrusion 2414 has a channelbore 2420 extending through a portion of the wedge protrusion 2414.While not necessary and depending on anatomical factors, the channelbore 2420 may be located halfway between the superior surface 2416 andthe inferior surface 2418. The wedge protrusion 2414 and through hole2406 are sized such that the base plate 2402 and wedge plate 2404 canabut, although in the typical implanted configuration, the base plate2402 and wedge plate 2404 would not in fact abut as the bone, e.g.spinous process, would intervene between the base plate 2402 and wedgeplate 2404 as shown in FIG. 57.

As best seen in FIGS. 56 and 57, the bores 2410 on attachment the tabs2408 generally align with the channel bore 2420 when the wedgeprotrusion 2414 resides in the through hole 2406 such that a connector2422 can extend through the bores 2410 and channel bore 2420 to connectthe base plate 2402 and wedge plate 2404 during use. Typically, theconnector 2422 comprises a screw and nut, but any conventional connectormay be used. When first implanted, the base plate 2402 and wedge plate2404 are aligned about a superior spinous process 2450 and an inferiorspinous process 2452. The connector 2422 connects the attachment tabs2408 and the wedge protrusion 2414. Ideally, but not necessarily, theconnector 2422 is not tightened and the base plate 2402 and wedge plate2404 may move with respect to each other, although in the initialcondition they can only move closer together. Once the plates arealigned with the proper distraction, the connector 2422 may be tightenedto lock the spinal implant 2400 in place. Ideally, but not necessarily,the supraspinous ligament remains intact to inhibit the spinal implant2400 from moving posteriorly out of the interspinous process space.Alternatively, and optionally, base plate 2402 and wedge plate 2404 maycomprise suture bores 2424 (FIG. 57). A suture 2426 may be connected tothe suture bores 2424 and traverse superior the spinous process 2450 andthe inferior spinous process 2452. Moreover, while only a pair of boresis shown with a pair of sutures, more may be provided. Moreover, thesuture 2426 should be construed generically to refer to cables, wires,bands, or other flexible biocompatible connectors. Such sutures may betied or locked using a tie, cable lock, or crimp.

FIG. 58 illustrates an alternative spinal implant 2500 similar in formand function to that of FIGS. 55-57. The spinal implant 2500 includes abase plate 2502 and a wedge plate 2504. The base plate 2502 includes anattachment tab 2506 and a bore 2508. The wedge plate 2504 has at leastone wedge prong 2510, but two wedge prongs 2510 are provided forimproved device stability. The two wedge prongs 2510 form a prongchannel 2512 to receive the attachment tab 2506 and provide someadditional stability. The wedge prongs 2510 have channel bores 2514.While both the attachment tab 2506 and the wedge prongs 2510 are shownas wedge shaped, both are not necessarily wedge shaped. The bore 2508and channel bores 2514 align such that a connector 2516 can be fittedbetween them to couple the base plate 2502 and wedge plate 2504together. Alternatively, the bore 2508 may be formed as a channel boreand the channel bores 2514 may be formed as a bore or they may all bechannel bores to allow for lateral adjustment of the plates.

FIG. 59 illustrates an alternative spinal implant 2600 similar to thatof FIG. 58 but instead of bores and connectors, protrusions 2602 areformed inside the prong channel 2604 and on the attachment tab 2606. Theprotrusions 2602 may be ribs, pins, shoulders, barbs, flanges, divots,detents, channels, grooves, teeth and/or other suitable protrusions. Theprotrusions 2602 may operate similar to a ratchet mechanism and may beconfigured so that the base plate and wedge plate can move towards eachother and distract adjacent bones, e.g. spinous processes. Theprotrusions 2602 engage such that the plates do not move apart afterthey are pressed together. The prong channel 2604 may be widened, e.g.by prying it open, to disengage the protrusions 2602 and allow theplates to be separated.

FIGS. 60-61 illustrate a spinal implant 2700. The spinal implant 2700includes a spacer having a spacer axis 2701, a first part 2702, and asecond part 2704. The first part 2702 has a main body 2706 with a firstend 2708 and a second end 2710. One or more lateral walls 2712 extendout from the first part 2702 transverse to the spacer axis 2701 at thefirst end 2708. The walls 2712 are adapted to extend along a superiorand inferior spinous process on a first side. The second end 2710 isadapted to reside in a space between the superior and inferior spinousprocess. The second part 2704 includes a main body 2714 and has a firstend 2716 and a second end 2718. One or more lateral walls 2720 extendout from the second part 2704 transverse to the spacer axis 2701 at thefirst end 2716. The walls 2720 are adapted to extend along a superiorand inferior spinous process on a second side. The second end 2718 isadapted to reside in a space between the superior and inferior spinousprocess. The lateral wall 2712, 2720 may be shaped to accommodateanatomy. The second end 2710 of the first part 2702 and second end 2718of second part 2704 abut or engage. A variety of features may beprovided to enhance this engagement. For example, the second ends mayinclude one or more channels and/or one or more protrusions that fit inthe channels. A set screw or the like may threadably engage a boreextending through the first and second parts to maintain them inalignment. However, as explained below, a set screw and bore areoptional. Interlocking channels and protrusions are optional as the endsmay just abut or have interfering surfaces. The ends may be slopedtransverse to the spacer axis 2701, as shown, to facilitate insertionand/or to increase the abutment area. Some alternate examples will bedescribed below relative to FIGS. 62-67.

Continuing with FIGS. 60-61, one or more through channels or bores 2722extend through the first and second parts 2702, 2704. A guidewire 2732extends through the channels 2722 generally parallel to the spacer axis2701. The guidewire 2732 may be formed of wire, braided or twisted cable(made of metallic or polymer strands), suture material, a flat metallicor polymer band (either braided or solid) and/or other suitablematerials and configurations. Multiple through channels may allow theguidewire 2732 to form a loop about the first end 2702 as shown in FIG.61. The guidewire 2732 ends may be connected around the second end suchas with a tie, crimp, knot, twist lock, cable lock, and/or othersuitable connections. When the guidewire 2732 is not looped, theguidewire 2732 may be locked against both the first and second endsusing a locking device such as a cable lock, crimp, knot, and/or anyother suitable locking device. The guidewire 2732 maintains the firstand second parts locked together.

FIGS. 62-63 illustrate a spinal implant 2800 similar to that of FIGS.60-61 except that it includes a protrusion 2804 extending from thesecond part 2704 to engage a slot 2802 extending from the first part2702 to stabilize the first and second parts relative to one another.

FIG. 64 illustrates a spinal implant 2900 similar to that of FIGS. 60-61except that the first part 2702 defines slot 2902 and the second part2704 tapers to a blade-like nose 2904 that engages the slot 2902.

FIGS. 65-66 illustrate a spinal implant 3000 similar to that of FIGS.60-6.1 except that the first part 2702 defines tapering side cutouts3002 separated by a central wedge shaped wall 3004 and the second part2704 tapers to a wedge shaped second end 3006. The wedge shaped secondend is divided by a groove 3008. When the first and second parts arepressed together, the wall 3004 engages the groove 3008 and the wedgeshaped second end 3006 engages the side cutouts 3002. Also, in theembodiment of FIGS. 65-66, the first and second parts 2702, 2704 haveone or more bores 3010, 3012 transverse to the spacer axis 2701 forreceiving a fastener to lock the parts together.

FIG. 67 illustrates a spinal implant 3100 similar to that of FIGS. 60-66and shown in the implanted condition. The first and second parts 2702,2704 are secured together with a single guide wire 3102 secured at eachend by a crimp 3104. Passageways 3106 are provided through the lateralwalls 2712, 2720. Sutures, wires, cables, bands, or other flexiblebiocompatible material 3108 may extend through the passageways 3106 andover and/or through a spinous process. The flexible biocompatiblematerial 3108 may loop under or over a single process (as shown on thesuperior process 3110), may loop around a single process (as shown onthe inferior process 3112), or may loop around both processes, or acombination thereof. The flexible biocompatible material 3108 may belocked using a locking device similar to those explained above. Theflexible biocompatible material 3108 and guidewire 3102 may optionallybe the same element.

FIG. 68 is a flowchart describing one exemplary methodology forimplanting the spinal implants of FIGS. 60-67. First, the patient isprepared for implanting the spinal implant, step 3202. Preparing thepatient may include, for example, making one or more incisions providingaccess to the spinal segment, placing the guidewire, etc. The surgicalsite is distracted (or measured as distraction may be caused by thespacer itself) using conventional distraction tools, step 3204. Onceexposed, the interspinous process space is prepared to receive thespinal implant, step 3206. This typically includes preparing the spinousprocesses to accept the spinal implant, which may include removing someportion of the spinous process, and removing muscle, tendons, andligaments that may interfere with implanting the spinal implant and/ormay provide force tending to unseat the spinal implant. The first partof the spinal implant is inserted, over or with the guidewire, to thesurgical site through the incision or the like, step 3208. Once at thesite, the first part of the spinal implant is positioned or aligned suchthat the lateral walls are loosely abutting a first side of the superiorand inferior spinous processes and the second end extends into theinterspinous space, step 3210. Generally, this means that the first partis implanted through the interspinous process space. The guidewire,which is attached to the first part of the spinal implant as explainedabove extends from the second end of the first part and is attached tothe second part of the spinal implant. Thus, the surgeon inserts thesecond part along the guidewire, step 3212. Note, the first part andsecond part may be positioned using tools or the surgeon may place theparts using hands and fingers. Using the guidewire, the protrusions (ifany) on the second part are inserted into the channels of the first part(if any) to align the first part and second part of the spinal implant,step 3214. Compressive force is applied to mate the first part and thesecond part, step 3216. The compressive force may be applied by crimpingthe guidewire, threading a cable lock, a separate clamp, or the like.Once sufficiently compressed, the first part and second part are lockedtogether, step 3218. Optionally, excess guidewire may be cut and removedor looped around the adjacent superior and inferior spinous process toprovide secured seating, step 3220. Once mated in the interspinousspace, the distraction of the spinal segment may be released, step 3222,and the patient's surgical site may be closed, step 3224.

FIG. 69 illustrates a spinal implant 3300. The spinal implant 3300,includes a superior spinous process seat 3302 and an inferior spinousprocess seat 3304. As shown, seats 3302 and 3304 form a U and inverted Ushape, but other shapes are possible including a square channel shapefor each seat, a C-shape, and/or any other suitable shape, although itis believed the saddle shape as shown would work well.

Seat 3302 includes a surface 3306 which contacts the superior spinousprocess and walls 3308 traversing each side of the superior spinousprocess to capture superior spinous process in seat 3302. Walls 3308 maybe convergent, divergent or relatively parallel. Walls 3308 may be moreakin to bumps, ribs, or shoulders to traverse only a minor portion ofthe spinous process or may be longer to traverse a major portion of thespinous process. Surface 3306 and walls 3308 may be discrete or shapedlike a saddle forming a smooth surface in which spinous process canrest. Attached to one wall 3308 is a vertical distraction post 3310extending towards inferior seat 3304. While only one verticaldistraction post 3310 is shown, multiple posts are possible. Moreover,if multiple posts are used, vertical distraction posts 3310 may resideon opposite sides of superior spinous process seat 3302. While shown asa straight post, vertical distraction post 3310 may be curved orstraight depending on anatomical considerations or the like.

Similar to seat 3302, seat 3304 includes a surface 3306 which contactsthe inferior spinous process and walls 3308 traversing each side of theinferior spinous process to capture inferior spinous process in seat3304. Attached to one wall 3308, on the side corresponding to verticaldistraction post 3310 is an attachment tab 3312. Attachment tab 3312 hasa vertical bore 3314 through which vertical distraction post 3310extends. Seat 3304 can be moved closer to or further from seat 3302along vertical distraction post 3310. Attachment tab 3312 also comprisesa horizontal bore 3316. Horizontal bore 3316 intersects vertical bore3314. A seating device 3318 is insertable into horizontal bore 3316. Asshown horizontal bore 3316 is threaded to accept a set screw or thelike.

In use, a surgeon would distract superior and inferior spinous processesand implant spinal implant 3300. Seats 3302 and 3304 would be set at adesired distraction and, for example, set screw 3318 would be threadedinto horizontal bore 3316 to apply seating force to seat verticaldistraction post 3310 in vertical bore 3314 locking seats 3302 and 3304at the set distraction distance.

Vertical distraction post 3310 and/or vertical bore 3314 may be arrangedwith a protrusion 3319 or detent to inhibit the ability of withdrawingvertical distraction post 3310 from vertical bore 3314.

FIG. 70 illustrates alternative seats 3400 and 3402. Seats 3400 and 3402are designed to nest or interlock. In that regard, seat 3400 has one ormore first blades 3404 or multiple surfaces spaced apart so first gaps3406 separate first blades 3404. Seat 3402 would similarly have one ormore second blades 3408 or multiple surfaces. Seat 3402 is shown with asingle second blade for convenience. Second plate 3408 is aligned withfirst gaps 3406 such that seats 3400 and 3402 may nest or interlock.Similarly, first blades 3404 could align with second gaps, not shown.Either first blades 3404 (as shown) or second blade 3408 may attach to avertical distraction post 3410 and second blade 3408 (as shown) or firstblades 3404 may attach to attachment tab 3412.

Although examples of a spinal implant and its use have been describedand illustrated in detail, it is to be understood that the same isintended by way of illustration and example only and is not to be takenby way of limitation. The invention has been illustrated in the form ofa spinal implant for use in spacing adjacent spinous processes of thehuman spine. However, the spinal implant may be configured for spacingother portions of the spine or other bones. Accordingly, variations inand modifications to the spinal implant and its use will be apparent tothose of ordinary skill in the art. The various illustrative embodimentsillustrate alternative configurations of various component parts such asspacers, retention members, additional fasteners, and the like. In mostcases, and as will be readily understood by one skilled in the art, thealternative configuration of a component part in one embodiment may besubstituted for a similar component part in another embodiment. Forexample, the differently shaped or expandable spacers in one example maybe substituted for a spacer in another example. Likewise the variousmechanisms for deploying a retention member or for providing additionalfasteners may be interchanged. Furthermore, throughout the exemplaryembodiments, where component part mating relationships are illustrated,the gender of the component parts may be reversed as is known in the artwithin the scope of the invention. The following claims are intended tocover all such modifications and equivalents.

1-72. (canceled)
 73. A spinal implant for placement between adjacentprocesses of a human spine, the spinal implant comprising: a spacerincluding a first end, a second end, a plurality of channels, and aspacer axis extending between the first end and the second end, theplurality of channels extending through the spacer parallel to thespacer axis; and a plurality of deployable retention members extendablethrough the plurality of channels.
 74. The spinal implant of claim 73,wherein each deployable retention member of the plurality of deployableretention members is adapted to grip one of the adjacent processes whendeployed through a channel of the plurality of channels.
 75. The spinalimplant of claim 74, wherein each deployable retention member is curvedto extend radially away from the spacer axis when deployed through achannel of the plurality of channels.
 76. The spinal implant of claim73, wherein the plurality of deployable retention members are axiallyslidable through the plurality of channels.
 77. The spinal implant ofclaim 73, wherein the plurality of deployable retention members areretractable during implantation of the spinal implant between adjacentprocesses.
 78. The spinal implant of claim 73, wherein the plurality ofdeployable retention members are straightenable for implantation of thespinal implant between adjacent processes.
 79. The spinal implant ofclaim 78, wherein each deployable retention member of the plurality ofdeployable retention members includes a stop to prevent completewithdrawal from a channel of the plurality of channels.
 80. The spinalimplant of claim 73, wherein each deployable retention member of theplurality of deployable retention members and each channel of theplurality of channels include complimentary rectangular cross sectionalshapes.
 81. The spinal implant of claim 73, wherein the spacer is hollowresulting in the spacer having an outer surface spaced from the spaceraxis.
 82. The spinal implant of claim 73, wherein the first end and thesecond end are tapered to facilitate implantation between adjacentprocesses.
 83. A spinal implant system for implanting a spinal implantbetween adjacent spinous processes, the system comprising: the spinalimplant including: a hollow body including a first end, a second end,and a longitudinal axis extending between the first end and the secondend, the first end and the second end including a plurality of channels;and a plurality of deployable retention members extendable through theplurality of channels and extending through the hollow body parallel tothe longitudinal axis*; and a implantation tube configured to contain atleast a portion of the spinal implant for positioning between theadjacent spinous processes.
 84. The spinal implant system of claim 83,wherein the implantation tube contains straightened portions of theplurality of deployable retention members for implantation between theadjacent spinous processes.
 85. A spinal implant comprising: a hollowbody adapted for implantation between adjacent spinous processes, thehollow body including a first end, a second end, and a longitudinal axisextending therebetween; and a plurality of deployable retention membersextendable through the hollow body and when deployed the plurality ofdeployable retention members extending radially away from thelongitudinal axis to grip at least a portion of each of the adjacentspinous processes.
 86. The spinal implant of claim 85, wherein the firstend and the second end each include a plurality of channels, eachchannel of the plurality of channels adapted to hold a portion of adeployable retention member of the plurality of deployable retentionmembers.
 87. The spinal implant of claim 86, wherein the plurality ofchannels operate to hold a portion of each deployable retention memberof the plurality of deployable retention members parallel to thelongitudinal axis as each deployable retention member extends throughthe hollow body.
 88. The spinal implant of claim 87, wherein theplurality of deployable retention members are axially slidable throughthe plurality of channels.
 89. The spinal implant of claim 87, whereinthe plurality of deployable retention members are retractable duringimplantation of the spinal implant between adjacent spinous processes.90. The spinal implant of claim 87, wherein the plurality of deployableretention members are straightenable for implantation of the spinalimplant between adjacent spinous processes.
 91. The spinal implant ofclaim 87, wherein each deployable retention member of the plurality ofdeployable retention members and each channel of the plurality ofchannels include complimentary rectangular cross sectional shapes. 92.The spinal implant of claim 87, wherein the first end and the second endare tapered to facilitate implantation of the hollow body betweenadjacent spinous processes.